This invention relates to resectoscopes and more particularly to an improved resectoscope and a novel cutting electrode for use with it.
Resectoscopes are surgical endoscopes for transurethral resection of the prostate gland or bladder growths and for the coagulation of bleeding vessels in the area of the prostate and bladder. The basic components of a resectoscope are a telescope, a working element assembly, a cutting electrode and a sheath. The sheath portion of the instrument is inserted in the urethra using an obturator which is then removed from it in order that the stem portion of the working element assembly with the telescope and cutting electrode can be mounted in the sheath. The telescope, typically about 4 mm. in diameter and about a foot long, lies in a snug yet slidable relationship in a channel in the stem portion of the working element assembly. It has a viewing system with an eyepiece at its proximal end and an objective lens at its distal end as well as means, such as a bundle of light carrying fibers or an incandescent lamp, for illuminating the telescope's field of view. The cutting electrode (typically formed of insulated tungsten wire between about 0.010 to 0.018 inches in diameter) is also carried by the working element assembly inside the sheath and has an uninsulated or bare arcuate cutting loop portion which is reciprocated forward and back through the sheath's fenestra in front of and within the field of view of the telescope.
The mechanical arrangement for reciprocating the electrode varies in different resectoscopes and forms no part of the present invention. Some instruments use a rack and pinion, others a spring and thumb control, while others use a fixed thumb position and move the electrode with the fingers via a movable block in the working element assembly. Cutting is accomplished by reciprocating the electrode while applying electrical high frequency currents to the electrode at voltages of between about 250 volts to about 4,000 volts or more at frequencies of from about 0.4MHz to about 3MHz. To facilitate clearing the telescope's field of view of the blood and other debris which tend to obstruct the doctor's view during resection, clear irrigation fluid is typically passed through the sheath and in front of the telescope's objective lens. In some resectoscopes a drain is also provided to allow continuous irrigation fluid flow through the sheath both in and out of the bladder.
Heretofore, insulation breakdown and capacitive coupling in resectoscopes in which the electrode is operated at the above indicated voltages and frequencies, has often caused accidental electrical burns to the doctor using the instrument and to the patient in whom the instrument is being used. Further, without an expensive stabilizer structure, prior art cutting electrodes used in such instruments lack adequate rigidity against upward and lateral deflection created by forces to which the electrode is subjected during resection. Without adequate rigidity, the extended electrode may be deflected out of the field of view, and the retracting electrode can be pushed out of alignment with the sheath, frequently contacting and burning the sheath's lower lip or causing electrical arcing between the electrode and the telescope. This often results in expensive damage to the latter and can cause termination of the surgical procedure. In addition, with prior art resectoscopes, the field of view is too often obscured by bubbles, blood and other debris which is not swept away by adequate irrigation flow, thus making uninterrupted operation of the instrument difficult.
One object of the invention, therefore, is to provide a new resectoscope which has substantially higher electrical safety than prior art devices and hence is less likely to cause accidental burns to either doctor or patient.
Another object is to provide a resectoscope with a high flow capacity continuous irrigation system which maintains a clearer visual field in front of the telescope and permits longer periods of uninterrupted operation of the instrument than heretofore.
Still another object is to provide a simple novel cutting electrode for use in the improved resectoscope.
A further object is to provide a novel resectoscope in which the cutting electrode loop is more adequately stabilized and supported in its path of travel than in prior art devices.
A still further object is to provide a novel resectoscope which maximizes the space inside the sheath available for irrigation fluid flow.
Yet another object is to provide a resectoscope in which: (a) the telescope is more effectively insulated from the ground or patient plate potential; (b) the size and number of exterior electrically conductive parts of the resectoscope are minimized; and (c) the capacitive coupling of these parts to the active conductors is reduced.
Further, other and additional objects and advantages of the invention will become apparent from the summary and detailed description of the invention which follow, as well as from the drawings and the appended claims.